Thin thermoluminescent dosimeter and method of making same

Abstract

An improved thermoluminescent ionizing radiation dosimeter of solid, extremely thin construction for more accurate low energy beta dosimetry is provided, along with a method of fabricating the dosimeter. In preferred forms, the dosimeter is a composite including a backing support (which may be tissue equivalent) and a self-sustaining body of solid thermoluminescent material such as LiF having a thickness of less than about 0.25 millimeters and a volume of at least about 0.0125 mm 3 . In preferred fabrication procedures, an initially thick (e.g., 0.89 millimeters) TLD body is wet sanded using 600 grit or less sandpaper to a thickness of less than about 0.25 millimeters, followed by adhesively attaching the sanded body to an appropriate backing. The sanding procedure permits routine production of extremely thin (about 0.05 millimeters) TLD bodies, and moreover serves to significantly reduce non-radiation-induced thermoluminescence. The composite dosimeters are rugged in use and can be subjected to annealing temperatures for increased accuracy.

We claim: 
     
       1. A radiation dosimeter comprising an essentially pure, self-sustaining, solid body of thermoluminescent material of substantially constant density and having a thickness of less than about 0.15 millimeters and a volume of at least about 0.0125 mm 3 . 
     
     
       2. The dosimeter of claim 1, said body having length and width dimensions of at least about 0.5 millimeters respectively. 
     
     
       3. The dosimeter of claim 2, said length and width dimensions being at least about 3 millimeters. 
     
     
       4. The dosimeter of claim 1, said thickness being less than about 0.05 millimeters. 
     
     
       5. The dosimeter of claim 1, said body presenting at least one sanded face. 
     
     
       6. The dosimeter of claim 1, said body presenting a pair of opposed sanded faces. 
     
     
       7. The dosimeter of claim 1, including a block for said body, and means for securing said body to said block. 
     
     
       8. The dosimeter of claim 1, said material being selected from the group consisting of  nat  LiF,  7  LiF,  6  LiF, Li 2  B 4  O 7 , CaSO 4 , CaF 2 , MgB 4  O 7 , doped species of the foregoing, and mixtures thereof. 
     
     
       9. The dosimeter of claim 1, said body having a volume of at least about 0.5 mm 3 . 
     
     
       10. The dosimeter of claim 9, said volume being from about 0.0125 to 2.5 mm 3 . 
     
     
       11. The dosimeter of claim 1, said body being in the form of a pressed or extruded initially powder material. 
     
     
       12. A method of fabricating a radiation dosimeter comprising the steps of: providing a solid, self-sustaining body of thermoluminescent material having a substantially constant density; and   physically abrading at least one surface of said body in order to reduce the thickness thereof to less than about 0.15 millimeters.   
     
     
       13. The method of claim 12, said abrading step comprising sanding at least one face of said body. 
     
     
       14. The method of claim 12, said abrading step comprising sanding a pair of opposed faces of said body. 
     
     
       15. The method of claim 12, said thickness being less than about 0.05 millimeters. 
     
     
       16. The method of claim 12, said body being selected from the group consisting of  nat  LiF,  7  LiF,  6  LiF, Li 2  B 4  O 7 , CaSO 4 , CaF 2 , MgB 4  O 7 , doped species of the foregoing, and mixtures thereof. 
     
     
       17. The method of claim 12, said body, after said abrading step, having a volume of at least about 0.0125 mm 3 . 
     
     
       18. The method of claim 12, said body, after said abrading step, having length and width dimensions of at least about 0.5 millimeters respectively. 
     
     
       19. The method of claim 12, including the step of attaching said abraded body to a block. 
     
     
       20. The method of claim 19, said attaching step comprising adhesively securing said abraded body to said block. 
     
     
       21. The method of claim 19, said block being approximately tissue equivalent material. 
     
     
       22. The method of claim 19, said block being non-tissue equivalent. 
     
     
       23. The method of claim 12, said body being substantially pure thermoluminescent material. 
     
     
       24. A radiation dosimeter produced by the method which comprises the steps of: providing a solid, self-sustaining body of thermoluminescent material having a substantially constant density; and   physically abrading at least one surface of said body in order to reduce the thickness thereof to less than about 0.15 millimeters.   
     
     
       25. A method of treating a solid thermoluminescent body comprising a crystalline ionic salt of the alkali metal and alkaline earth metals, said method comprising the step of physically abrading a surface of said body to an extent that the body exhibits at least about a factor of two reduction in non-radiation induced thermoluminescence, as compared with an otherwise identical, unabraded body. 
     
     
       26. The method of claim 23, said abrading step comprising sanding said surface of said body.